Adjunctive zonisamide for weight loss in euthymic bipolar disorder patients: a pilot study

Abstract

Objective: To assess the effectiveness and tolerability of open adjunctive zonisamide in treatment of obesity in euthymic bipolar disorder (BD) patients.

Method: Zonisamide was administered to recovered, overweight BD outpatients assessed with the Systematic Treatment Enhancement Program for Bipolar Disorders (STEP-BD) Affective Disorders Evaluation and followed with the STEP-BD Clinical Monitoring Form. Weight changes (Body Mass Index (BMI) and BMI percentage changes) were assessed prospectively at four weekly visits, one bi-weekly visit, and then five monthly visits, for a maximal duration of six months. Weight loss was assessed with random effects modeling to maximize all available data for analysis.

Results: Twenty-five BD (10 BD-type I, 15 BD-type II) patients (mean age 41.0+/-10.4 years, 64% female, 96% Caucasian) on a mean of 2.8+/-1.5 prescription psychotropic and 1.3+/-1.4 prescription non-psychotropic medications received zonisamide for a mean duration of 14.2+/-8.5 weeks, with a mean final dose of 375+/-206 (range 75-800) mg/day. Slope of weight loss was 0.078 BMI points per week, and non-zero (p<0.0005). Mean weight loss was 1.2+/-1.9 BMI points (baseline BMI 34.2+/-3.1 to final BMI 33.0+/-3.5, p<0.003). Eighteen patients (72%) discontinued study participation early, 11/25 (44%) due to emergent mood symptoms (eight depression, two mania, one subsyndromal mixed symptoms) requiring treatment intervention, 5/25 (20%) due to adverse physical events, and 2/25 (8%) due to patient choice, but none due to weight loss inefficacy.

Conclusion: Adjunctive zonisamide appeared effective and generally physically tolerated, but had high rates of mood adverse events, in obese BD patients. Controlled trials are warranted to systematically explore these preliminary naturalistic observations.